The purpose of this project is to determine the magnitude and duration of acetylcholinesterase inhibition in cerebrospinal fluid after a single oral 3.0-mg dose of SNZ ENA 713 ad ministered to healthy elderly volunteers, and patients very early in the course of Alzheimer's disease (AD). ENA 713, an acetylcholinesterase (AChE) inhibitor of the carbamate type, is being investigated as a symptomatic treatment for AD. ENA 713 enhances cholinergic transmission in the central nervous system (CNS) by preventing the breakdown of acetylcholine, the neurotransmitter system most prominently compromised in AD. It is postulated that ENA 713, (as has been shown to be true of other similar cholinesterase inhibitors: taurine, physostigmine), may reverse some of the deficits seen in AD. It is hoped that ENA 713 may offer an advantage to the AD patient in being less hepatoxic than taurine, and may be better tolerated than alternate therapy such as physostigmine. In the preceding CRC-based study of ENA 713 the method of continuously and safely sampling CSF during a 49-hour period of lumbar catheterization was established. This study proposes to extend this technical approach to the normal elderly (of any gender) and to establish the viability of this technique in patients with AD. In this regard two elderly normal subjects, and six very early in the course of illness, will participate.